The present invention concerns a bearing arrangement, and, more particularly, to a bearing arrangement for gearbox shafts in a change-speed gearbox of the countershaft type for motor vehicles, in which a main drive shaft permanently driven by a drive motor is connected to a coaxial input shaft by a selector clutch, used for changing gear and the shaft end, of a coaxial output shaft, opposite to the input shaft is both rotatably supported and fixed so that it cannot move relative to the gearbox casing in the directions of the axis of rotation in a casing wall of a gearbox casing by way of a rolling contact bearing arrangement configured as a fixed location bearing, and in which each of the two shaft ends of the input shaft is supported by a rolling contact bearing arrangement relative to the adjacent shaft ends of the main drive shaft and the output shaft.
In a known bearing arrangement as shown in SU 11 64 088 A, a central input shaft end opposite to the crankshaft, which generally has a fixed location bearing, of the drive motor can be both brought into drive connection by a clutch and be supported by a rolling contact bearing arrangement arranged as a fixed location bearing. The output end, i.e. the shaft end located opposite to the input shaft, of a coaxial output shaft forming the gearbox output is supported in a rear casing wall of the gearbox casing by a rolling contact bearing arrangement arranged as a fixed location bearing. On their shaft ends facing towards one another, the input and output shafts are supported relative to one another by a rolling contact bearing arrangement arranged as a floating bearing.
In this known bearing arrangement, high axial forces appear at the two fixed location bearings of the input and output shafts, particularly where helical teeth are provided on the gear stages which bring these two shafts into drive connection with the countershaft, which is usually parallel thereto.
These axial forces are disadvantageous because the fixed location bearings are located on the casing side so that the axial forces occur at the casing with each of the absolute rotational speeds of the shafts and, in addition, generate unpleasant noises in the gearbox casing. A further disadvantage in the known bearing arrangement is caused by the occurrence of axial clearance between the input shaft and the output shaft due, among other things, to installation tolerances, axial forces and the different temperature expansion coefficients of the shafts and the casing.
An object on which the present invention is based consists essentially in providing a bearing arrangement which avoids the above-mentioned disadvantages.
The object has been achieved in an advantageous manner by arranging the rolling contact bearing arrangement of the adjacent shaft ends of the input shaft and the output shaft as a fixed location bearing so that the input shaft and the output shaft are fixed substantially immovably relative to one another in the directions of the axis of rotation.
In the bearing arrangement of the invention, any axial clearance between the input shaft and the output shaft is removed per se because only one casing-side fixed location bearing remains and the axial forces due to the helical teeth are accepted, on one hand, by the reaction forces on the fixed location bearing between the input shaft and the output shaft and, on the other, by the tooth forces of the gearwheels connected to the countershaft, i.e. they are not transferred to the casing-side fixed location bearing in the gearbox casing.
The present invention applies generally both to so-called simple change-speed gearboxes, in which one and the same input shaft is located in the force path between the main drive shaft and the output shaft in all gears. The invention also relates to change-speed gearboxes of the multi-path type in which at least two input shafts are provided; these paths can be selected during gear changes by the engagement of a respectively associated selector clutch--with a corresponding change in the force path between the main drive shaft and the output shaft.
When the invention is used in a simple change-speed gearbox, in which the selector clutch is connected to a drive pinion of a gearwheel stage for driving the countershaft by an input shaft of short axial length, there is the additional advantage that eccentricity errors in the crankshaft are not transmitted to the drive pinion.
Another advantageous feature of the present invention is a short installation length.
Yet another advantageous feature of the present invention is in twin-path change-speed gearboxes with a central first input shaft and a second input shaft designed as a hollow shaft and arranged concentrically with the first input shaft.
In a further advantageous embodiment of the invention, for a twin-path change-speed gearbox, axial clearance between the two input shafts is avoided, axial forces being also kept away from the casing-side rolling contact bearing arrangement of the second input shaft designed as a hollow shaft.